1. Field of the Invention
The present invention relates generally to devices for protecting electronic components that are sensitive to electrostatic discharge (ESD). The present invention also relates to procedures for handling, shipping, storing and/or assembling such sensitive components. Examples of electrostatic discharge sensitive components include Si bipolar and MOSFET devices, and GaAs MESFET devices, and other devices.
2. Discussion of the Related Art
Electrostatic discharge sensitive components may require special handling while they are shipped, stored, assembled, etc. to avoid being damaged. Sometimes the components must be handled in class 1 or higher rooms to avoid degradation or damage due to electrostatic discharge. The required special handling may increase the cost of manufacturing the larger systems, such as circuit boards, that incorporate such components. In addition, the cost of replacing electronic components damaged by electrostatic discharge may increase the total cost of the manufacturing process.
Electrostatic discharge sensitive components are particularly susceptible to damage before they are electrically inserted into a larger system (such as a circuit board). Once the leads of the electronic component are electrically connected to the larger system, there is less risk of damage, since the gate/base, source/emitter and drain/collector leads are no longer the only paths for electrostatic discharge currents. Consequently, there is a need in the art for protective devices and procedures for protecting electrostatic discharge sensitive components prior to assembly of such components into circuit boards and the like.
It has been suggested to strap the terminals of component devices together by a series of thermocompression attached gold (Au) wire bonds, to dissipate electrostatic charges that could otherwise build up on the terminals. This thermocompression bonding process would be costly, however, both in terms of the required materials and the labor required to assemble and subsequently remove the wire bonds. In addition, it would be difficult to remove the bonds after the component devices are inserted into larger systems.
Others have suggested the use of packaging films with conductive slivers to protect sensitive electronic components. Such films are referred to in U.S. Pat. Nos. 5,314,732 and 5,165,985 (Wiste). The packaging films described in the Wiste patents would not be fully satisfactory, however, because they would not ensure electrical contact with the leads of the packaged component. Moreover, the packaging film would have to be at least partially removed from the component during assembly of the component into a circuit board. Consequently, the component would be susceptible to electrostatic discharge damage or degradation during the time while it is being assembled into the circuit board.
Other devices for providing electrostatic discharge protection are shown in U.S. Pat. No. 5,773,876 (Mekdhanasarn), U.S. Pat. No. 5,746,621 (Cronin), U.S. Pat. No. 5,652,410 (Hobbs), U.S. Pat. No. 5,163,850 (Cronin), and U.S. Pat. No. 5,108,299 (Cronin).
There is a need in the art for an uncomplicated, easy-to-use device or system for protecting electrostatic discharge sensitive components. There is also a need in the art for a convenient method of protecting such components while they are being assembled into circuit boards and the like.
The disadvantages of the prior art are overcome to a great extent by providing a protective device for protecting a packaged electronic component. According to one aspect of the invention, the protective device has a support structure for installation on the packaged electronic component and conductive material formed on said support structure for providing electrical connection between the electronic component""s leads.
According to another aspect of the invention, the protective device has adhesive material for adhering the support structure to the electronic component.
In a preferred embodiment of the invention, the protective device has an opening for receiving a portion of the packaged electronic component, and the adhesive material and the conductive material are in thin rings surrounding the opening. The adhesive material may be a pressure sensitive adhesive. The conductive material may be a layer of electrodeposited metal, and the invention may be practiced with other suitable materials.
According to yet another aspect of the invention, the support structure may be formed of a flexible sheet of polymeric material.
The present invention also relates to a method of protecting an electrostatic discharge sensitive electronic component. The method includes the steps of connecting a support structure to the exposed conductive leads of the electronic component, and placing the leads in electrical contact with conductive material formed on the support structure. In a preferred embodiment of the invention, the support structure is adhesively connected to the leads, and a top portion of the electronic component extends through an open space in the center of the support structure.
According to one aspect of the invention, the protective structure is removed from the electronic component after the component is electrically connected to an electronic device such as a circuit board. This way, the electronic component remains protected from electrostatic discharge throughout the manufacturing process.
The present invention also relates to the combination of an electronic component and a protective device assembled on the electronic component. The invention is applicable to a wide variety of electronic components, including components with different leads configurations and also taped components. An advantage of the invention is that protective devices of a single size and configuration may be used to protect several different types of electronic components.
The present invention also relates to a taped electronic components assembly. The assembly may include conductive layers formed on a tape structure. The conductive layers remain with the tape structure when the electronic components are connected to a circuit board or the like.
In an alternative embodiment of the invention, protective devices are associated with individual electronic components, and a series of such protected components are supplied on a tape structure.
These and other features and advantages of the invention will become apparent from the following detailed description of preferred embodiments of the invention.